# Dark sectors and enhanced $h\to \tau \mu$ transitions

## TL;DR

This paper explores how extended decay topologies involving dark sectors can mimic flavor-violating Higgs decays, impacting LHC search interpretations and connecting to dark matter and muon g-2 anomalies.

## Contribution

It introduces a three-body decay model with dark-sector mediators that can explain multiple phenomena and affect Higgs decay search strategies.

## Key findings

- Dark sector mediators can produce signals similar to flavor-violating Higgs decays.
- The model accounts for dark matter, lepton mass structure, and muon g-2 anomalies.
- Extended decay topologies can broaden mass distributions in Higgs decay searches.

## Abstract

LHC searches with $\tau$ leptons in the final state are always inclusive in missing-energy sources. A signal in the flavor-violating Higgs decay search, $h\to\tau\mu$, could therefore equally well be due to a flavor conserving decay, but with an extended decay topology with additional invisible particles. We demonstrate this with the three-body decay $h\to\tau\mu\varphi$, where $\varphi$ is a flavorful mediator decaying to a dark-sector. This scenario can give thermal relic dark matter that carries lepton flavor charges, a realistic structure of the charged lepton masses, and explain the anomalous magnetic moment of the muon, $(g-2)\mu$, while simultaneously obey all indirect constraints from flavor-changing neutral currents. Another potentially observable consequence is the broadening of the collinear mass distributions in the $h\to \tau\mu$ searches.